Hydraulic drive means for a swinging door or the like



Oct. 3, 1967 G. HUGLE 3,344,555

HYDRAULIC DRIVE MEANS FOR A SWINGING DOOR OR THE LIKE Filed Oct. 18,1965 f/ME REVERE/1V6 fi Inventor:

Goikard -fli/ &

United States Patent 3,344,555 HYDRAULIC DRIVE MEANS FOR A SWINGING DOOROR THE LIKE Gebhard Hiigle, Aach-Linz, near Pfullendorf, Germany FiledOct. 18, 1965, Ser. No. 497,388 a 12 Claims. (Cl. 49-340) The presentinvention relates to hydraulic drive means for turning a door or thelike in which movement of an hydraulic piston is transmitted by means ofa linkage arrangement to the door for turning the latter about a turningaxis.

It is an object of the present invention to provide hydraulic drivemeans for turning a door or the like about a turning axis between twoend positions in which the drive means are constructed and arranged tofixedly hold the door in either of the tWo end positions thereof so thatseparate locking means or holding means for holding the door in eitherof the two end positions thereof become unnecessary.

It is an additional object of the present invention to provide forhydraulic drive means of the aforementioned kind which are extremelycompact in construction so as to require relatively little space.

It is a further object of the present invention to provide for drivemeans of the aforementioned kind which are composed of relatively fewand simple parts so that the whole arrangement can be constructed atvery reasonable cost and will stand up perfectly under extended use.

With these objects in view, the arrangement of the present inventionmainly comprises support means, a door mounted on the support meansturnably between two end positions about a turning axis, a cylindermember, a piston member movable in the cylinder member between oppositeends thereof and including a piston rod projecting with one end thereofbeyond the cylinder member, in which one of the two members is pivotallymounted at one end thereof to the support means. The arrangementincludes further means for feeding a fluid under pressure into one endof the cylinder member and for discharging the fluid from the oppositeend thereof and vice versa for reciprocating the piston member in thecylinder member, lever means mounted on the support means pivotableabout a pivot axis and pivotally connected at a portion thereof to thatend of the other of the two members which is farthest from the end atwhich said one member is pivotally mounted on the support means to bemoved between two end positions during movement of the piston memberbetween the ends of the cylinder member, elongated substantiallystraight guide means pivotally connected at one end thereof to thesupport means for pivoting movement about a tilting axis, said guidemeans having a length at least equal to the distance between the pivotaxis and a free end of said lever means and being operatively connectedto the door for turning the latter about the turning axis during tiltingmovement of the guide means, and engaging means projecting from saidfree end of the lever means and engaging the guide means for tilting thelatter about the tilting axis during pivotal movement of the levermeans. The lever means and guide means are arranged with respect to eachother and to the door in such a manner so that, in either end positionof the lever, the door will be in a corresponding end position and sothat the portion of the lever means between the pivot axis and said freeend thereof includes in either end position of said lever means an angleof substantially 90 with the guide means, whereby the door will befixedly held in either end position and can be moved only by feedingpressure fluid into one end of the cylinder member and dischargingpressure fluid from the other end thereof.

3,344,555 Patented Oct. 3, 1567 The lever means is preferably atwo-armed lever having a shorter and a longer arm including an acuteangle with each other.

Separate locking means for the door become therefore unnecessary, and inaddition thereto the door will make during opening and closing thereof aharmonic motion.

The aforementioned arrangement may be constructed either in such amanner that the elongated guide means is connected by means of a lengthadjustable linkage to the door and this arrangement is especiallyadvantageous if the drive means have to be installed on an alreadyexisting door whereby the adjustable linkage permits to adapt the drivearrangement in a convenient manner to the available space and to theexisting structural arrangement.

On the other hand, the guide means may be arranged with respect to thedoor in such a manner that the tilting axis of the guide means coincideswith the turning axis of the door and in this arrangement the one end ofthe guide means is fixedly connected to the door in the region of theturning axis of the latter.

An especially compact arrangement is derived when the support meansincludes an elongated substantially rectangular support plate on whichthe guide means and the two-armed lever are respectively pivotallymounted in the region of diagonally opposite corners of the plate and in'which the cylinder member, likewise mounted on the plate, has an axiswhich includes with a diagonal connecting the pivot points of the guidemeans and the lever an acute angle.

According to a further feature of the present invention the means forfeeding the fluid under pressure into the cylinder preferably include apump, a pair of conduits connecting the pump to opposite ends of thecylinder member, an electromotor operatively connected to the pump fordriving the same, means for starting and stopping the motor andincluding an electrical time delay so adjusted that after the motor isstarted it will be automatically shut off by the time relay after a timeperiod slightly longer than that necessary to move the door between theend positions thereof. Preferably, an adjustable pressure release valveis provided in each of the conduits.

Due to this arrangement it is possible to arrest the door in anyposition without the danger of damaging the drive motor or any of theconnecting elements. This arrangement makes also separate stop switchesengaged by the door in either of the end positions thereof and incircuit with the motor for disconnecting the same when the door reacheseither of its end positions unnecessary, and the door may be simplystopped in either of its end positions by mechanical means provided forinstance at opposite ends of the guide means. This arrangement has alsothe advantage that, if movement of the door should be stopped by anyresistance before it reaches its end position, for instance byaccumulated snow, the pressure fluid fed by the pump into the cylinderwill be discharged through the adjustable pressure relief valve andafter a predetermined time the motor will be stopped by the time relayso that further feeding of pressure fluid to the cylinder will likewisestop.

Since the pressure relief valves are individually adjustable it ispossible to adjust the maximum force exerted by the drive means on thedoor during the closing movement of the latter in a manner slightlydifferent from the maximum force exerted by the drive means on the doorduring the opening movement of the same. Preferably the arrangementincludes also adjustable regulating means in each of the counduitsconnecting the pump to the opposite ends of the cylinder memberconstructed and arranged in such a manner for letting fluid freely passfrom the pump to the cylinder member and for adjustably regulating flowof fluid from the cylinder member to the pump. This makes it possible toregulate the speed of the door closing movement in a manner differentfrom that of the door opening movement. This arrangement in which theflow of the pressure fluid from the pump to the cylinder member is notthrottled in any way, so that the full pressure produced by the pumpwill be maintained in the conduits, has also the advantage thatunderpressure or inclusion of air in the conduits will be avoided, whichcould otherwise be produced when extraneous forces, for instance windpressure, act on the door tending to move the door with a speed greaterthan that produced by the drive means.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a partial top view of one modification of the arrangementaccording to the present invention in which the means for feedingpressure fluid into and out of the cylinder member are onlyschematically illustrated; and

FIG. 2 is a partial top view of another embodiment of the arrangementaccording to the present invention, drawn to a smaller scale than FIG.1, and wherein the pressure fluid feeding means are omitted.

The arrangement illustrated in FIG. 1 includes a door T mounted on abracket fixed to a pillar 2 of a building construction and turnable inthe bracket between an open end position, shown in full lines in FIG. 1,and a closed end position, shown in dash-dotted lines, about a turningaxis 3 extending along one side edge of the door. The means for turningthe door T between the end positions are mounted on an elongatedsubstantially rectangular support plate 1 which may be connected in anyknown manner to the rear side of the pillar 2. These means include acylinder member 8 pivotally mounted at 9 in the region of a closed endthereof on the plate 1. A piston member, now shown in the drawing, isslidably mounted in the cylinder member 8 and the piston member includesa piston rod 18 projecting beyond the other end of the cylinder member.A two-armed lever 6, 19 is pivotally mounted between the ends thereof at7 on the support plate 1 and the short arm 19 of the two-armed lever,which includes an acute angle with the longer arm 6 thereof, ispivotally connected at the free ends thereof to the free outer end ofthe piston rod 18. Engaging means project from the free end of thelonger arm 6 and these engaging means may include a pivot pin 10projecting in substantial normal direction from the free end of the arm6 and a roller 11 turnably mounted on the pivot pin 10. The engagingmeans 10, 11 project upwardly and engage in a groove formed in anelongated substantially straight guide means 4 pivotally connected atone end thereof at to the support plate 1 so that the roller 11 isslidably guided in the groove of the guide means 4 and so that duringtilting of the two-armed lever 6, 19 about its pivot axis 7 theelongated guide means 4 is likewise tilted about its pivot axis 5. Theopposite ends of the groove in the elongated guide means 4 are closedand the end opposite to the end at which the elongated guide means 4 ispivoted is closed by a connecting member 12 fixedly connected to thisend of the guide means, for instance by welding. The connecting member12 extends transverse to the axis of the elongated guide means 4 and isprovided at the opposite ends thereof with a pair of bores 13 and 14 andan elongated linkage means 15 is pivotally connected at one end thereofto the bore 13 of the connecting member 12. The other bore 14 of theconnecting member 12 may be used for connecting the linkage means 15thereto in an arrangement in which the drive means are located on theside of the door opposite from 4 the side thereof shown in FIG. 1. Theother end of the linkage means 15 is pivotally connected to a connectingbracket 16 fixedly connected in any convenient manner to one side faceof the door T spaced from the pivot axis 3 thereof. The linkage means 15are preferably adjustable in length and these linkage means may includea rod 15 provided at opposite ends with an external right hand and lefthand thread, respectively, which are respectively engaged into sleevemembers 15" provided with correspondingly directed internal threads andrespectively pivotally connected to the connecting member 12 and to thebracket 16 so that during turning of the rod 15 about its axis thelength of the linkage means 15 and therewith the angular position of thedoor T with respect to the elongated guide means 4 may be adjusted. Therod 15' may be provided with a bore therethrough to facilitate turningof the same about its axis. The end of the support plate 1 adjacent tothe pillar 2 is preferably provided with a cutout in which the closedend of the cylinder 8 is pivotally mounted and the arrangement is madein such a manner that the elongated guide means 4, the linkage means 15and the double-armed lever 6, 19 are mounted as close as possible abovethe cylinder member 8. The elongated guide means 4 and the lever 6, 19are respectively pivotally mounted in the region of diagonally oppositecorners of the support plate 1, whereas the axis of the cylinder member8 extends substantially in longitudinal direction of the elongatedsupport plate 1 so that the axis of the cylinder member 8 and the pistonrod 18 aligned therewith includes an acute angle with a diagonalconnecting the pivot points 5 and 7 of the guide means 4 and thetwo-armed lever 6, 19, respectively. This provides for a very compactconstruction of the arrangement.

The means for feeding pressure fluid, preferably pressure oil, intoopposite ends of the cylinder 8 and for discharging the pressure fluidtherefrom comprise a pair of conduits 21 and 22 each flexibly connectedat one end thereof to the respective end of the cylinder memoer 8 andeach communicating over a one-way suction valve 24 with the interior ofa container B filled with oil. The conduits 21 and 22 communicateintermediate the ends thereof with opposite ends of a reversible pump23, which may be in the form of a gear pump, and which may be driven bymeans of a reversible electromotor M connected to the gear pump 23 inany convenient manner for rotating the same. Communicating with each ofthe conduits 21 and 22 is also an adjustable pressure release valve 25by means of which the pressure of the pressure oil furnished from thepump 23 to the cylinder member 8 may be adjusted. The arrangementincludes also adjustable regulating means 26 and 27 respectivelyarranged in the conduits 21 and 22 intermediate the ends thereof. Theadjustable regulating means 26 includes a bypass 28 provided with aone-way valve through which oil under pressure may flow freely from thepump 23 to the one end of the cylinder 8 and an adjustable throttlepassage 30 through which flow from the aforementioned end of thecylinder 8 to the pump 23 may be throttled. The regulating means 27include also a bypass 29 with a oneway valve permitting free flow fromthe pump 23 to the other end of the cylinder member and an adjustablethrottle passage 31 for the return flow of the fluid from the other endof the cylinder member 8 to the pump 23. The throttle passages 30 and 31may be individually adjusted, whereby movement of the piston in thecylinder in the one or the other direction may be individually adjustedfor adjusting the opening and closing time of the door.

The arrangement is illustrated in full lines in FIG. 1 in a position inwhich the door T is fully open. In this one end position of the door,the double-armed lever 6, 19 is also in one of its end positions and theengaging means 10, 11 on the free end of the longer lever arm 6 are atone end of the groove in the elongated guide means 4 abutting againstthe connecting member 12 afiixed to the one end of the guide means 4. Asshown in FIG. 1; in this end position of the lever 6, 19 the longer arm6 thereof includes an angle beta of substantially 90 with the axis ofthe elongated guide means 4 and in this position of the elongated guidemeans 4 and the arm 6 of the two-armed lever any forces tending to turnthe elongated guide means about the pivot axis 5 thereof will be takenup by the arm 6 so that turning of the elongated guide means 4 or thedoor connected thereto by extraneous forces, for instance wind forcesacting on the door, will not be possible. The door T will therefore belocked in the open position and can be moved only by feeding pressurefluid into one end of the cylinder 8 and simultaneously dischargingpressure fluid from the other end thereof. 4

A time relay 31 and a switch 32 are arranged in circuit with the motorM, as schematically shown in FIG. 1. The switch 32 is constructed andarranged in a known manner in circuit with the time relays 31 and themotor M so that during each closing of the switch 32 the time relay 31is started and the direction of the motor M is reversed. The time relay31 is adjusted in such a manner so as to shut off the motor M againafter passing of a time period which is slightly longer than necessaryto move the door normally between the end positions thereof.

The arrangement above described will operate as follows:

If the door T is to be moved from the open position shown in full linesin FIG. 1 to the closed position thereof shown'in dash-dotted lines, theswitch 32 is closed, starting thereby the time relay 31 and theelectromotor M which will drive the gear pump 23 in the direction asindicated by the arrow A to pump thereby pressure oil through the bypass29 of the conduit 22 into the end of the cylinder member 8 which isopposite the end thereof at which the cylinder member 8 is pivotallymounted on the support plate 1. The piston rod 18 is thereby retractedinto the cylinder member 8, turning thereby the two-armedlever 6, 19 incounterclockwise direction so that the engaging means 10, 11 fixed tothe free end of the longer arm 6 of the two-armed lever will move alongthe groove in the elongated guide means 4 to turn the latter inclockwise direction about the pivot axis 5 thereof whereby this turningmovement of the elongated guide means 4 will be gradually acceleratedand subsequently thereto gradually decelerated until the guide means ismoved to the end position as shown in dash-dotted lines in FIG. 1.Turning of the elongated guide means 4 about its pivot axis 5 will'betransmitted over the linkage 12, 15 and 16 to the door '1 which willbemoved thereby from the open position, shown in the full lines, to theclosed position, shown -in dashdotted lines, in which further movementof the door will be stopped, since in this end position of the door Tand the elongated guide means 4 the axis of the elongated guide meansextends also normal to the longer arm 6 of the double armed lever due tothe fact that the length of the arm 6 is chosen substantially identicalto that of the groove in the elongated guide means 4. In the closedposition of the door T the latter will be also held in fixed position bythe linkage connected thereto. When the door reaches its closedposition, the pump will still be operated for a short time until thetime relay 31 shuts off the motor M. During this time pressure fluidpumped by the pump 23 will be discharged through the pressure reliefvalve 25 connected to the conduit 22.

The pressure oil which during the closing movement of the door will bedischarged from the cylinder passes from the latter through the conduit21 and has to flow through the throttled passage 30 in this conduitwhereby the adjusted open cross section of the throttled passage 30 willdetermine the maximum speed of the closing movement of the door. Theabove described sequence of operations will be reversed during reopeningof the door.

If the above described arrangement is to be used on a 6. door having twowings, then two drive units as above described are used, whereby thecylinder members 8 of the two units are preferably supplied withpressure fluid from a common pump connected by two conduits as describedabove to the cylinder of each drive unit, each of the conduits providedwith adjustable regulating means in the manner as described above.

As mentioned above, the provision of the time relay makes separateelectrical stop switches, engaged by the door in the end positionsthereof, unnecessary. The described arrangement is thereby considerablyimproved over arrangements known in the art since such stop switcheswhich are mounted in the open are liable to fail, especially during snowor rain. A separate overload switch for protecting the motor is also notnecessary since the running time of the motor determined by the timerelay will be usually shorter than the operating time of an overloadswitch.

FIG. 2 illustrates another embodiment of the present invention at asmaller scale. The arrangement shown in FIG. 2 differs from thearrangement shown in FIG. 1 mainly in that the pivot axis of theelongated guide means 4 in this arrangement coincides with the turningaxis 3 of the door T and in that the elongated guide means is fixedlyconnected to the door T in the region of the tuming axis of the latter.A separate linkage arrangement 12, 15, and 16, as shown in FIG. 1,between one end of the elongated guide means and the door becomestherefore unnecessary in the arrangement shown in FIG. 2. Otherwise, thearrangement shown in FIG. 2 is substantially identical with that shownin FIG. 1 and elements of the arrangement shown in FIG. 2 performing thesame function as the corresponding elements illustrated in FIG. 1 aretherefore designated with the same reference numeral. It is to beunderstood that the conduits 21 and 22 schematically and only partlyindicated in FIG. 2 are provided with the same devices and furnishedwith pressure fluid in the same manner as described in connection withFIG. 1.

While in FIG. 2 the elongated guide means 4 are shown to be connected tothe door T to be substantially aligned with the same, it is obvious thatthis arrangement may be modified if necessitated by the construction ofthe pillar 2 or for some other reasons in such a manner that theelongated guide means 4, while fixedly connected to the door T, mayinclude an angle of less than with the latter.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofhydraulic drive means for turning a door dilfering from the typesdescribed above.

' While the invention has been illustrated and described as embodied inan hydraulic drive means for turning a door in which the drive means isconstructed to lock the door in opposite end positions thereof, it isnot intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An arrangement of the character described, comprising in combination,support means; a door mounted on said support means turnably between twoend positions about a turning axis; a cylinder member; a piston membermovable in said cylinder member between opposite ends thereof andincluding a piston rod projecting with one end thereof beyond saidcylinder member, one of said two members being pivotally mounted at oneend thereof to said support means; means for feeding a fluid underpressure into one end of said cylinder member and for discharging thefluid from the opposite end thereof and vice versa for reciprocatingsaid piston member in said cylinder member; lever means mounted on saidsupport means pivotable about a pivot axis and pivotally connected at aportion thereof to that end of the other of said two members which isfarthest from the end at which said one member is pivotally mounted onsaid support to be moved between two end positions during movement ofsaid piston member between the ends of said cylinder member; elongatedsubstantially straight guide means pivotally connected at one endthereof to said support means for pivoting movement about a tiltingaxis, said guide means having a length at least equal to the distancebetween said pivot axis and a free end of said lever means and beingoperatively connected to said door for turning the latter about saidturning axis during tilting movement of said guide means; and engagingmeans projecting from said free end of said lever means and engagingsaid guide means for tilting the latter about said tilting axis duringpivotal movement of said lever means, said lever means and guide meansbeing arranged with respect to each other and to said door in such amanner that in either end position of said lever means said door is in acorresponding end position and the portion of said lever means betweensaid pivot axis and said free end thereof includes an angle ofsubstantially 90 with said guide means, whereby said door will befixedly held in either end position and can be moved only by feedingpressure fluid into one end of said cylinder member and dischargingpressure fluid from the other end thereof.

2. An arrangement as set forth in claim 1, wherein said cylinder memberis the said member pivotally mounted at one end thereof on said supportmeans and wherein said piston rod is the other said member that projectsbeyond the other end of said cylinder member and is pivotally connectedat the free end thereof to said lever means.

3. An arrangement as set forth in claim 2, wherein said lever means is atwo-armed lever, having a longer and a shorter arm, said engaging meansprojecting from the free end of said longer arm, and said free end ofsaid piston rod being pivotally connected to the free end of saidshorter arm.

4. An arrangement as set forth in claim 3, wherein said two arms of saidlever includes an acute angle with each other.

5. An arrangement as set forth in claim 4, and said operative connectionincluding linkage means pivotally connected at opposite ends thereof tosaid door and to the other end of said guide means.

6. An arrangement as set forth in claim 5, wherein the length of saidlinkage means is adjustable.

7. An arrangement as set forth in claim 4, wherein said support meansincludes an elongated substantially rectangular support plate, saidguide means and said twoarmed lever are respectively pivotally mountedin the region of diagonally opposite corners of said plate, and saidcylinder member, likewise mounted on said plate, having an axisincluding with the diagonal connecting the pivot points of said guidemeans and said lever an acute angle.

8. An arrangement as set forth in claim 1, wherein said turning axis ofsaid door coincides with said tilting axis of said guide means andwherein said one end of said guide means is fixedly connected to saiddoor in the region of said turning axis.

9. An arrangement as set forth in claim 1, wherein said means forfeeding the fluid under pressure into said cylinder member include apump, a pair of conduits conmeeting said pump to opposite ends of saidcylinder member, a motor operatively connected to said pump for drivingthe same, means for starting and stopping said motor and including timermeans so adjusted that after the motor is started it will beautomatically shut off by said timer means after a time period slightlylonger than that necessary to move said door between said end positionsthereof.

10. An arrangement as set forth in claim 9, wherein said motor is areversible electric motor, and wherein said timer means is an electricaltime relay.

11. An arrangement as set forth in claim 10 and including an adjustablepressure relief valve in each of said pair of conduits.

12. An arrangement as set forth in claim 11 and including adjustableregulating means in each of said conduits constructed and arranged forletting fluid freely pass from said pump to said cylinder member and foradjustably regulating flow of fluid from said cylinder member to saidpump.

References Cited UNITED STATES PATENTS 1,716,567 6/ 1929 Shonnard 491372,550,349 4/1951 HelZ 49-340 3,244,415 4/ 1966 Lunenschloss et a1. 52 X3,301,313 1/1967 Schurink 188 3,302,330 2/1967 Loftus 49137 X DAVID J.WILLIAMOWSKY, Primary Examiner.

J. K. BELL, Assistant Examiner.

1. AN ARRANGEMENT OF THE CHARACTER DESCRIBED, COMPRISING IN COMBINATION,SUPPORT MEANS; A DOOR MOUNTED ON SAID SUPPORT MEANS TURNABLY BETWEEN TWOEND POSITIONS ABOUT A TURNING AXIS; A CYLINDER MEMBER; A PISTON MEMBERMOVABLE IN SAID CYLINDER MEMBER BETWEEN OPPOSITE ENDS THEREOF ANDINCLUDING A PISTON ROD PROJECTING WITH ONE END THEREOF BEYOND SAIDCYLINDER MEMBER, ONE OF SAID TWO MEMBERS BEING PIVOTALLY MOUNTED AT ONEEND THEREOF TO SAID SUPPORT MEANS; MEANS FOR FEEDING FLUID UNDERPRESSURE INTO ONE END OF SAID CYLINDER MEMBER AND FOR DISCHARGING THEFLUID FROM THE OPPOSITE END THEREOF AND VICE VERSA FOR RECIPROCATINGSAID PISTON MEMBER IN SAID CYLINDER MEMBER; LEVER MEANS MOUNTED ON SAIDSUPPORT MEANS PIVOTABLE ABOUT A PIVOT AXIS AND PIVOTALLY CONNECTED AT APORTIONS THEREOF TO THAT END OF THE OTHER OF SAID TWO MEMBERS WHICH ISFARTHEST FROM THE END AT WHICH SAID ONE MEMBER IS PIVOTALLY MOUNTED ONSAID SUPPORT TO BE MOVED BETWEEN TWO END POSITIONS DURING MOVEMENT OFSAID PISTON MEMBER BETWEEN THE ENDS OF SAID CYLINDER MEMBER; ELONGATEDSUBSTANTIALLY STRAIGHT GUIDE MEANS PIVOTALLY CONNECTED AT ONE ENDTHEREOF TO SAID SUPPORT MEANS FOR PIVOTING MOVEMENT ABOUT A TILTINGAXIS, SAID GUIDE MEANS HAVING A LENGTH AT LEAST EQUAL TO THE DISTANCEBETWEEN SAID PIVOT AXIS AND A FREE END OF SAID LEVER MEANS AND BEINGOPERATIVELY CONNECTED TO SAID DOOR FOR TURNING THE LATTER ABOUT SAIDTURNING AXIS DURING TILTING MOVEMENT OF SAID GUIDE MEANS; AND ENGAGINGMEANS PROJECTING FROM SAID FREE END OF SAID LEVER MEANS AND ENGAGINGSAID GUIDE MEANS FOR TILTING THE LATTER ABOUT SAID TILTING AXIS DURINGPIVOTAL MOVEMENT OF SAID LEVER MEANS, SAID LEVER MEANS AND GUIDE MEANSBEING ARRANGED WITH RESPECT TO EACH OTHER AND TO SAID DOOR IN SUCH AMANNER THAT IN EITHER END POSITION OF SAID LEVER MEANS SAID DOOR IS IN ACORRESPONDING END POSITION AND THE PORTION OF SAID LEVER MEANS BETWEENSAID PIVOT AXIS AND SAID FREE END THEREOF INCLUDES AND ANGLE OFSUBSTANTIALLY 90* WITH SAID GUIDE MEANS, WHEREBY SAID DOOR WILL BEFIXEDLY HELD IN EITHER END POSITION AND CAN BE MOVED ONLY BY FEEDINGPRESSURE FLUID INTO ONE END OF SAID CYLINDER MEMBER AND DISCHARGINGPRESSURE FLUID FROM THE OTHER END THEREOF.